Algorithmic Approach To Stridor

graph TD
    A([Stridor in a Child]) --> B{Assess Severity}

    %% Severity Branching
    B -->|Severe / Life-Threatening| C[Severe Distress<br/>Lethargy, SpO2 < 92%, Cyanosis, Bradycardia]
    C --> D[EMERGENCY ACTION<br/>1. Provide O2, keep child calm<br/>2. DO NOT examine throat/use tongue depressor<br/>3. Call Anesthesia & ENT<br/>4. Secure Airway in OR/ICU]

    B -->|Mild to Moderate| E[Stable Airway<br/>Alert, SpO2 > 92%, Mild/No retractions]
    E --> F{Onset & Duration}

    %% Acute vs Chronic
    F -->|Acute| G{Presence of Fever?}
    F -->|Chronic / Recurrent<br/>Months/Congenital| H{Clinical Features}

    %% Acute Febrile
    G -->|Febrile| I{Clinical Presentation}
    I -->|Low fever, Barking cough, Gradual, Nontoxic| J[Viral Croup]
    J --> J_Tx[Mild: Oral Dexamethasone<br/>Mod/Severe: Neb L-Epinephrine + Dexamethasone]

    I -->|High fever, Rapid onset, Toxic, Drooling, Tripod| K[Acute Epiglottitis]
    K --> K_Tx[DO NOT examine throat<br/>Intubation in OR/ICU<br/>IV Ceftriaxone +/- Vancomycin]

    I -->|High fever, Biphasic, Toxic, Barking cough, Tracheal tenderness| L[Bacterial Tracheitis]
    L --> L_Tx[Rigid Bronchoscopy & Suction<br/>Intubation + IV Broad-spectrum Abx]

    I -->|High fever, Gradual, Toxic, Neck stiffness, Muffled voice| M[Retropharyngeal Abscess]

    %% Acute Afebrile
    G -->|Afebrile| N{History & Exam}
    N -->|Sudden choking episode| O[Foreign Body Aspiration]
    O --> O_Tx[Rigid Bronchoscopy<br/>Heimlich if immediate obstruction]
    N -->|Other Causes| P[Anaphylaxis / Spasmodic Croup / Trauma / Hypocalcemia]

    %% Chronic
    H -->|Worsens supine/crying/feeding,<br/>Onset weeks to 6 months| Q[Laryngomalacia<br/>*Most Common*]
    Q --> Q_Tx[Conservative / PPI for GERD<br/>Supraglottoplasty if severe]

    H -->|History of prematurity/prolonged intubation| R[Subglottic Stenosis]
    R --> R_Tx[Endoscopy to Grade<br/>Dilation / Laryngotracheal reconstruction]

    H -->|Cutaneous hemangiomas in beard distribution| S[Subglottic Hemangioma]
    S --> S_Tx[Propranolol monitoring]

    H -->|Worsens on neck flexion| T[Vascular Rings]
    H -->|Weak/breathy cry| U[Vocal Cord Paralysis / Laryngeal Web]

    %% Investigations Link
    E -.-> V[<b>Key Diagnostics when stable:</b><br/>- AP X-ray: Steeple sign Croup<br/>- Lateral X-ray: Thumb sign Epiglottitis<br/>- Awake Flex Laryngoscopy: Chronic causes<br/>- Bronchoscopy: FB / Tracheitis / Stenosis sizing]
    
    %% Styling
    classDef emergency fill:#ffcccc,stroke:#ff0000,stroke-width:2px,color:#000;
    classDef diagnosis fill:#e1f5fe,stroke:#0288d1,stroke-width:1px,color:#000;
    classDef treatment fill:#e8f5e9,stroke:#388e3c,stroke-width:1px,color:#000;
    class C,D emergency;
    class J,K,L,M,O,Q,R,S,T,U diagnosis;
    class J_Tx,K_Tx,L_Tx,O_Tx,Q_Tx,R_Tx,S_Tx treatment;

Definition And Pathophysiology

• Indicates acute or chronic upper respiratory tract obstruction.
• Characterized by high-pitched, harsh, or metallic/brassy sounds.
• Produced by turbulent airflow across narrowed segments of respiratory tract.
• Airway resistance inversely proportional to fourth power of airway radius.
• Minor reductions in cross-sectional area exponentially increase airway resistance and work of breathing.
• Anatomic factors predisposing infants include small laryngeal size, loose submucous connective tissue around glottis, and rigid cricoid cartilage encircling subglottic zone.
• Cricoid cartilage represents narrowest portion of upper airway in children under 10 years.

Classification

Anatomic Classification Based On Respiratory Phase

Etiological Classification

Acute Stridor

Chronic Or Recurrent Stridor

• Laryngeal Causes:
  • Laryngomalacia: Most common, collapse of supraglottic structures during inspiration.
  • Congenital Subglottic Stenosis: Second most common, cricoid diameter <3.5 mm in term newborn.
  • Vocal Cord Paralysis: Third most common, bilateral or unilateral.
  • Congenital Subglottic Hemangioma: Associated with cutaneous beard-distribution hemangiomas.
  • Laryngeal Webs/Atresia: Failure of laryngeal recanalization.
  • Laryngoceles And Saccular Cysts: Abnormal fluid/air-filled dilations.
• Tracheobronchial Causes:
  • Tracheomalacia/Bronchomalacia: Chondromalacia causing insufficient cartilage support.
  • Vascular Rings: Extrinsic compression.
  • Mediastinal Masses: Lymphangioma, bronchogenic cysts, congenital goiter.

Clinical Evaluation

History

• Onset And Duration: Acute onset suggests infection or foreign body. Onset at birth suggests severe anatomic anomaly. Onset at 2 weeks peaking at 6 months suggests laryngomalacia or hemangioma.
• Triggers And Modifying Factors: Worsened by feeding, crying, or supine position indicates laryngomalacia. Worsened by neck flexion indicates vascular ring.
• Associated Symptoms:
  • Barking cough, coryza indicates viral croup.
  • Dysphagia, drooling, toxic appearance indicates epiglottitis.
  • Cutaneous hemangiomas indicate subglottic hemangioma.
  • Breathy cry indicates unilateral vocal cord paralysis or laryngeal web.
• Birth History: Prematurity, prolonged intubation indicates acquired subglottic stenosis.

Severity Assessment

Specific Physical Signs

• Tripod Posture: Sitting upright, leaning forward, chin thrust forward, mouth open indicates acute epiglottitis.
• Preferred Posture: Neck hyperextension preferred in vascular rings or retropharyngeal abscess.
• Drooling And Dysphagia: Strongly points towards supraglottic pathology.
• Tracheal Tenderness: Specific to bacterial tracheitis.

Differential Diagnosis Of Acute Infectious Causes

Diagnostic Investigations

General Precautions

• Avoid invasive/painful procedures in young children with impending airway obstruction.
• Postpone intravenous access attempt or blood tests until stabilized.
• Do not use tongue depressors or examine oral cavity directly if epiglottitis suspected.
• Do not sedate child until airway secured.

Imaging Modalities

• Anteroposterior Neck Radiograph: Demonstrates steeple sign in croup and bacterial tracheitis.
• Lateral Soft-Tissue Neck Radiograph: Demonstrates thumb sign in epiglottitis. Shows enlarged prevertebral space in retropharyngeal abscess.
• Chest Radiograph (Inspiratory/Expiratory): Expiratory films helpful in foreign body aspiration revealing obstructive emphysema, air trapping, mediastinal shift.
• Barium Swallow: Evaluates vascular rings, slings, and tracheoesophageal fistulas.
• CT/MRI Scan: High-resolution CT delineates aberrant anatomy.

Endoscopy

• Awake Flexible Laryngoscopy: Gold standard for diagnosing laryngomalacia and vocal cord paralysis.
• Direct Laryngoscopy And Rigid Bronchoscopy:
  • Essential for diagnosis and sizing of congenital subglottic stenosis.
  • Mandatory for diagnosis and management of bacterial tracheitis.
  • Definitive modality for removal of foreign bodies.
  • Must be performed in controlled settings with anesthetist and otolaryngologist present.

Laboratory Studies

• Complete Blood Count shows neutrophilic leukocytosis in bacterial causes.
• Blood and surface cultures indicated only after securing airway in epiglottitis/tracheitis.

Management Principles

Initial Stabilization

• Ensure minimal handling.
• Keep baby on mother's lap.
• Administer supplemental oxygen in non-threatening manner to maintain SpO2 >95%.
• Emergency call for anesthesiologist and otolaryngologist if signs of severe airway obstruction present.

Specific Interventions

Viral Croup

• Mild: Single dose oral dexamethasone (0.6 mg/kg) or nebulized budesonide (2 mg). Discharge with parental counseling.
• Moderate-To-Severe:
  • Hospitalization preferable.
  • Nebulized L-epinephrine (undiluted 1:1000, dose 0.5 mL/kg, max 5 mL). Constricts precapillary arterioles reducing edema.
  • Mandatory systemic corticosteroids (Dexamethasone 0.6 mg/kg max 8 mg) to prevent rebound after epinephrine wears off.
  • Observe for minimum 4 hours.

Foreign Body Aspiration

• Immediate Heimlich maneuver if complete laryngeal obstruction.
• Prompt removal via rigid bronchoscopy under general anesthesia.

Congenital And Chronic Lesions

• Laryngomalacia: Conservative management. Anti-reflux medication for concurrent GERD. Supraglottoplasty indicated for severe cases including cyanosis, cor pulmonale, failure to thrive.
• Subglottic Stenosis: Endoscopic dilation/laser for mild cases. Anterior cricoid split or laryngotracheal reconstruction for severe grades.
• Subglottic Hemangioma: Propranolol (1-3 mg/kg/day). Monitor for hypoglycemia and bradycardia.
• Saccular Cysts/Laryngoceles: Endoscopic CO2 laser excision or marsupialization.
• Vascular Rings/Masses: Surgical excision or division of offending structures.